Equipment cabinets are commonly used to store telecommunications and networking equipment found at many sizeable businesses today. Such equipment cabinets are often provided in a tall and narrow configuration, housing equipment stacked vertically to conserve floor space. One such standard cabinet configuration is about 72 inches tall by about 22 inches wide. It is common for these equipment cabinets to include front and rear panel doors to provide a uniform appearance, shield unsightly clutter, protect devices housed therein from environmental hazards, and restrict unauthorized access.
During a seismic event, these equipment cabinets are often subject to violent forces. Such forces can cause the cabinet to move in one or more directions. Tall cabinets are particularly susceptible to lateral movements, as they tend to deform the rack, at least temporarily. The deformation is due at least in part to inertia of heavy equipment located in a top portion of the cabinet.
Lateral movement of the cabinet's base, combined with inertia of top-mounted equipment, produces torque along sidewalls of the cabinet. This torque can cause the rectangular cabinet to sway, resulting in deformation to a non-rectangular, parallelogram. For standard equipment racks that are deeper than they are wide, the deformation is often pronounced along the front and rear sides. Unfortunately, these sides are the ones most often fitted with panel doors.
The equipment cabinet doors are typically attached to the cabinet frame with two or more hinges located along one of the vertical sides. One or more latches are also provided along the opposite vertical side to secure the door in a closed position. Because the doors are typically rigid and often made of steel, they tend to maintain their original shape as the cabinet deforms to a non-rectangular parallelogram. The resulting difference in shapes creates stresses and strains at the points of attachment. Namely, forces are focused at the hinges and the latches, causing one or more of the hinges and latches to fail during the seismic event and the panel door to open or detach from the cabinet altogether.
Such an open or unattached cabinet door, particularly during the seismic event, could lead to injury of nearby personnel and to potential damage to other surrounding equipment. Open or unattached cabinet doors can also pose additional obstacles that may hamper rescue efforts following the seismic event.
The need for designing structurally sound equipment cabinets in view of a seismic event of a predetermined magnitude is recognized. One such standard adopted to qualify testing of equipment cabinets is NEBS GR-63-CORE. Unfortunately, designing equipment cabinets to meet the stringent seismic requirements often leads to added complexity and cost.